The proposed research is an interdisciplinary, intedepartmental collaborative effort to enable us to explore local cerebral glucose metabolism in the brain of man and how it is altered in various physiologic and pathologic situations. Such an exploration is now possible for the first time due to the development of the 18F-fluorodeoxyglucose method for the measurement of local cerebral glucose metabolism in man. There is extensive data in the literature suggesting a close link in the brain among functional activity, metabolism and blood flow. Thus, with an increase in functional activity in a region of the brain due to a specific stimulus one would expect an increase in the local metabolic rate and local perfusion. The proposed studies thus will not only provide us with important new information concerning local cerebral glucose metabolism per se, but also can be used to map the regions of the brain that are activated by a specific stimulus. The physiologic stimuli to be investigated are visual and cognitive tasks. In addition, the effects of pathologic conditions on local cerebral metabolism and local cerebral perfusion will be examined. These conditions are stroke, epilepsy, Alzheimer's disease, and brain tumor.